Electrode.



UNITED STATE@ PATENT oEEieE. l

GUs'rAv w. ELMEN, or scHENEcfrAnY, YORK, AssIGNoR rro GENERAL ELECTRIC COMPANY, .A G'ORPRATION 0F NEW YoRK.-

ELno'rnonE.

specificati@ of Letters Patent.

Patented Mar. 25,1913.

Application filed August 80,1906. Serial No. 332,583.

Sweden, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electrodes, of Vwhich the following is a specification.

This invention relates to electrodes, and more particularly to that general class ofl electrodes used for producingwhat4 are known as luminous or fian'iing arcs.

In general, my invention consists in adding tothe material of the electrodes hereinafter specified a small quantity of a vaporizable 'compound for 'the purpose of steadying the arc and preventing the tiickerings and 'light variations which sometimes arise with electrodes of the flaming arc type.

I have found that sodium compounds are especially suited as arc-steadying ingredients, and although some sodium compounds appeal' to have a greater power than others, the following are typical of the general class included in lmy invention z-sodium nitrate; sodium chlorate; sodium carbonate; sodium bichromate and sodium fiuorid. .Of these compounds, I consider sodium `luorid the most suitable, and I have found that even a very small quantity of this material in the electrode effects wonderful rresults a steadying means.

The body of the electrode with which the sodium steadying compound is associated may consist of a variety of materials giving a luminous or fiaming arc, but of thisgeneral class, electrodes consisting substantially of titanium compounds, such as Athe carbid or oxid, or of mixtures of titanium compounds with iron compounds, are typical.

In order that my invention may be better understood I have hereinafter described it as applied to so-called magnetite electrodes containing magnetic oXid of iron, titanium bxid and chromite. Such electrodes may be made by mixing and grinding together thirty parts of. rutile, seventy parts of magnetite and twelve and o'ne-half parts of chromite. It is to this mixture, or to similar. mixtures of-which this one is typical, that I add a small quantityof asodium compound to'steady the alrewhen the electrode lis in use. v .Unsteadiness in the are may result from ysente a smooth and son'iewhat rounded surone-{of several diferentcauses, and although ,i

I do not consider it necessary to explain in detail why the lamp is unsteady lor why it flickers, I havevhereinafter pointed out two sources of unsteadiness, and have explained how the sodium compound is used to over come these undesirable features. t

In the accompanying drawing', Figure l is a'longitudinal section of an electrode embodying my invention, sho\\'ing the upper' end of the electrode it appears after run ning vamfew hours in a lamp; Fig. 2 is an elevation of two electrodes showing the arc between them as produced in accordance with my invention.

Flaming arc electrodes may be of various formsand sizes 'and may be manufactured in different ways, but the species shown in Fig. lV is typical. It consists of a sheet iron envelop l. having a metal closure?, at the bottom, and containing a,tilling 3 of the electrode material. When this filling is to consist of chi-omite, n'lagnetite and rutile, in the proportions heretofore mentioned, l mix with it approximately one-quarter of one per cent. sodium tluorid, adding this material before the' mixing and grinding opera tion, so that it may ybecome intimately asso ciated with the other eon'lpone'nts.l This mixture may .be moistened with water to render it somewhat plastic and may lbe packed or tamped into the sheet iron tube l.y When the electrodeis in use, this sheet iron envelop melts and wastes away with the filling so that the end of the electrode preface. If the lamp is extinguished after several hours of operation, the hot material at the'V end of the electrode forms a smooth and dense cap over the end of the electrode. This cap is however sufficiently conductive to permit re-lighting of the arc without diiiculty.

When an electrode composed of the'material above indicated, but without the addition of sodium fluor-id, is operated, a Vpit or crater is formed in the 'lower electrode,

which becomes deeper and wider as thel operation of the lamp continues; and in eX- treme cases the upper end of the electrode may become entirely `hollowed out, After the arc has `been maintained forfabout 18 hours, the crater disappears and the `end ofv y the electrode assumesjthe general .jcontoury shown in Fig. 1 but during thejitime.. that the crater forms andpelsitfthej apexvyof `ldie are shifts about on the edge-of the pit or crater and the'light luctuates in a very fannoymg manner.

`In addition to the source of instability above mentione`d,there is another source whichI prefer to .designate as Wandering of the arc. `not contain the sodium compound yield an are which meanders about over the electrode,

apparent-ly seeking a new location for the cathode spot. This migration of the arc is cents-and although I may depart somewhat fromfthis proportion,A I consider it. advisable toi-keep the quantity of sodium fluorid low. `If too" much 1s added the compound appears to causea fusion or melting down of the end Voil? the electrode in such a way that when the lamp is stopped, a substantially non-conducting-button forms on the end of the electrode and the lamp will not again start until this button is removed. One-quarter of one per cent. of sodium fluorid does not change the color of the arcappreciably, although, of course,:the presence ot sodium can be detected with 'a spectroscope. Another reason exists why the proportion of sodium com.

' pound .should be kept low, and that is the peculiar lifting of the luminous` cone of the are whichl takes place when ythe electrode containsan excess of the sodium compound. Fig. .4r `represents diagrammatically a luminous are running under normal conditions.

From the upp'er elect-rode 7 depends a cone shaped :1i-e8 theapex of which just touches the top ofvthcnegatlvo electrode t). 'l`h1s I'tind that electrodes which dov cone is the source of a large amount of the light radiated by the are, although the vapors which surround the cone are also luminous. In Case the electrode contains an excess of the sodium compound, or in case compounds of other metals are substituted, there is a tendency for this luminous cone 8 to periodically lift or be forced away from the negative electrode 9. The lifting of the cone is `'only momentary and produces not-hing more serious than an instantaneous decrease in light intensity, but as this decrease may amount to as much as titty per cent. of the entire light delivered by the are, the phenomenon is objectionable. The immediate cause of this change in the luminous cone is obscure.' With some electrodes the cone never lifts, with others it may lift only once a night, while with others it may lift every tire or six minutes throughout theentire life of the electrode. Whatever the cause of this instability may be, I find that a sodium compound lsuch as sodium fluorid may safely be used with the electrode mixture in the proportion of one-quarter of one per cent., without danger of causing any appreciable lifting of the arc cone, or 1n fact, any objectionable phenomena.

hat l claim as new and desire to secure by Letters latent of the United States, is,

l. A metallic liamiug are lamp electrode containing substantially o11e,qi1:1i'ter of one per cent. sodium tluorid.

L. Au are lamp electrode consisting oi a metal tube and a lilling there-tor composed of a mixture ot' iron oxid, rutile and chromite and about one-quarter of one per cent. et' sodilm tluorid.

Si. .\u essentially metallic are light pencil comprising fluorid ot' an alkaline metal.

ln witness lua-col'` l have hereunto set m\' hand this 25th day ot August. ltltlt.

\\' i t uesses 

